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`stat -f` on GNU coreutils is --file-system, a boolean flag rather than a format option, so `stat -f %m <marker>` treats both arguments as operands. It exits 1 on the bogus `%m` operand -- so the `||` fallback does fire -- but it has already written a multi-line filesystem block to stdout, which the command substitution captures alongside the fallback's epoch. The arithmetic on the following line then dies under `set -u` with "File: unbound variable". On Linux this left the CronCreate PreToolUse gate dead before it could emit exit 2, stopped the PostToolUse hook from capturing ad-hoc crons into the registry, and aborted writeback.sh set-alive/audit for the duration of a SessionStart reconcile. Swap to GNU-first, matching the convention already used in bin/cron-from.sh and hooks/scope-trust-legacy-warn.sh. On BSD `stat -c` fails cleanly with no stdout, so this order is unambiguous. Refs crisandrews#36 Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Fixes the Linux breakage reported in #36.
The bug
All three marker-age checks probe
stat -f %mbefore falling back tostat -c %Y. On GNU coreutils-fis--file-system, a boolean flag, not a format option — sostat -f %m <marker>treats%mand the marker as two operands. It exits 1 on the bogus%m, so the||fallback does fire, but it has already written a multi-line filesystem block to stdout. The command substitution captures that block alongside the fallback's epoch, and the arithmetic on the next line dies underset -uwithFile: unbound variable.Impact on Linux
hooks/cron-pretool.sh— the CronCreate gate dies before it can emit exit 2hooks/cron-posttool.sh— ad-hoc crons are never captured into the registryskills/crons/writeback.sh—set-alive/auditabort for the duration of a SessionStart reconcileNet effect: cron reconcile is unreliable on Linux, which is a plausible contributor to the orphan-entry symptom in #32.
The fix
Swap the probe order to GNU-first. This is the convention already used in
bin/cron-from.shandhooks/scope-trust-legacy-warn.sh— the latter from your own commitfix(hooks): scope-trust legacy-warn crashed on GNU/Linux (stat -f is --file-system, not format). This PR applies that same correction to the three sites it didn't reach.The order is unambiguous in both directions: on BSD,
stat -cfails cleanly with no stdout, so the fallback to-f %mworks exactly as before.Three lines, no behaviour change on macOS.
Testing
Verified on Debian (GNU coreutils 9.x, bash 5.2): before the change, a SessionStart reconcile aborted with
File: unbound variable; after it, reconcile completes and the registry audit reportsalive=2/2 orphaned=0. Confirmed again in normal use over the past two days.macOS path unchanged and untested by me — worth a second pair of eyes there, though
stat -cfailing with empty stdout on BSD is well documented.🤖 Generated with Claude Code